Quote:
Originally Posted by sahilkhokhar
Five years ago , the average age of p and q was 15 years, average age of p, q and r today is 20 years, how old will r be after 10 years.
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5 years ago, average age of p & q was:
(We are subtracting 5 as it was 5 years ago & dividing by 2 as it was their average age.)
{(p-5)+(q-5)}/ 2 = 15
(p+q-10)/2 = 15
Multiply by 2 on both sides
p+q-10 = 30
p+q= 30+10
p+q= 40 -------- Equation (I)
Average age of p,q & r today:
(Dividing by 3 as it is average age of 3)
(p+q+r)/3 = 20
Multiply by 3 on both sides
p+q+r = 60 ------ Equation (II)
Now subtract equation I from equation 2
p+q+r = 60
- p+q = 40
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r = 20
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present age of r= 20 years
age of r after 10 years= 20+10
age of r after 10 years= 30 years